Test change mechanism for a vending machine

Question: Ask applicant to test a change mechanism for a vending machine. Specification - input = nickels, dimes, quarters and dollar bills, price range of items is 55 to 75 cents.
Answer: A good candidate should cover many of the different testing methodologies with this question and should be coming up with interesting/creative test cases in relatively rapid succession for 5 minutes or more. No hires generally run out of ideas within 1-4 minutes. An exceptional candidate may think of different test cases for 15 minutes or more. Some of the various test areas and possible answers are listed below:

Functional: testing all combinations of coins for 55 and 75 cents. For example, 11 nickels, 5 dimes and a nickel, 2 quarters and a nickel, 1 dollar...any combination that adds up to 55 cents and the same for 75 cents. Advanced testers may think of designing a finite-state diagram to cover all combinations. Test change return option as well.

Boundary: no input value, less than expected value (i.e. less than 55 cents), more than expected value (i.e. $2.00).

Stress: Excessively high input values. For example, if I inserted 10 dollars worth of dimes, how does the machine respond? What if I run out of nickels for change, how does the machine detect this and distribute change. What is the wear and tear on the internal mechanism over time. Will machine function constantly/reliable for 10 years. What if the machine is full with a particular change value. For example, dimes and the machine cannot accept any more dime values. What about environmental stress conditions such as extreme heat or cold, or altitude changes. How does it respond to rain.

Error: No change available in machine. Is customer notified. If I input invalid coins, how does the machine react (i.e. pennies). What if I unplug and plug in the machine to simulate a power outage. Does it reset itself? Does it remember input values up to that point? What if machine can't accept any value since it is so full it requires service.

Security: Use of crowbar to attempt to open machine. What about a photocopied dollar bill. Is this accepted by machine?

Performance: Does the system respond quickly even under stress conditions listed above.

Usability: Is everything clearly labeled? Do customer's understand how to use change mechanism?

Accessibility: Can a blind person use the system? Does system have brail?

Localization: Can system be reset to accept coins from different countries? For example, Canada, Japan?

Integration Testing: Applicant may consider testing coin mechanism in conjunction with other parts.